Data Repository Space Security Unusual Behavior in GEO: SJ-17 Last UpdatedApril 4, 2019 By Thomas G. Roberts ShareView in the Data Repository This data repository accompanies Space Threat Assessment 2019, a featured report from the CSIS Aerospace Security Project. This data repository visualizes the orbital position of Chinese satellite SJ-17 from January to September 2018, relative to other satellites currently in the GEO belt. Unlike most objects in the geostationary belt, SJ-17 made a series of orbital maneuvers after it reached its destination orbital regime, varying its position relative to the Earth and neighboring satellites. In 2018, SJ-17 occupied a wide span of positions on orbit, from 37.7°E (corresponding to an orbital position overlooking eastern Africa) to 180°E (corresponding to an area overlooking the U.S. Marshall Islands). In early 2018, defense news outlet Breaking Defense published a detailed list of SJ-17’s movements—provided by Analytical Graphics, Inc., an engineering software company—including a list of satellites that may have engaged directly with it through remote proximity operations (RPO).1 An adapted version of the table appears below. Show Timeline of Orbital Maneuvers Time Period Action November 3, 2016 Launch of SJ-17 November 3 – 11, 2016 Initial GEO drift November 12, 2016 Rendezvous with Chinasat 5A at 165°E November 13 – December 28, 2016 Proximity operations with Chinasat 5A December 29, 2016 – April 24, 2017 Maintained orbit nearby Chinasat 5A April 25 – June 19, 2017 Relocated to 125°E June 20 – September 29, 2017 Parked next to Chinasat 6A September 29 – October 8, 2017 Relocated to 118°E October 9, 2017 – January 11, 2018 Maintained orbit January 11, 2018 Initiated eastward drift February 10, 2018 Rendezvous with Chinasat 20 February 11 – March 16, 2018 Proximity operations with Chinasat 20 (as the pair drifted westward from ~176°W to ~40°E)2 March 17 – April 14, 2018 Relocated to 115° E To learn more about the potential consequences of such behavior on orbit, including a broader look at China’s counterspace weapon activities, read the China space threat assessment in Space Threat Assessment 2019. Methodology This data visualization relies on two principal data sources: the Space-Track.org catalog of all space objects, provided by the U.S. Strategic Command’s Combined Space Operations Center (CSpOC),3 and a database of geostationary satellites currently on orbit, provided by NY2O.com.4 The orbital position data for SJ-17 from January to September 2018—shown in orange in the interactive diagram—was derived from the two-line element (TLE) data for the satellite, available at Space-Track.org. The TLE for a space object is a measurement of the object’s approximate orbit (its inclination, right ascension of the ascending node, eccentricity, and argument of perigee) and its position on that orbit (its mean anomaly). This data was transformed into a time-dependent longitude position using PyEphem, a publicly-available Python package for high-precision astronomy computations.5 Although Space-Track.org provides more than one TLE for SJ-17 per day during the time period depicted, this data repository shows just one longitudinal position per day, for clarity. Other data points were excluded at the author’s discretion. The orbital position data for the other GEO satellites—shown in gray in the interactive diagram—use data from NY2O.com, as it appeared on March 24, 2019. This interactive data repository is a product of the Andreas C. Dracopoulos iDeas Lab, the in-house digital, multimedia, and design agency at the Center for Strategic and International Studies. Special thanks to Jacque Schrag for her work developing this tool.